Chenmou Elm is a small deciduous tree native to Anhui and Jiangsu provinces in eastern China, where it is found at elevations below 200 m on the Langya Shan and Baohua Shan mountains . Growing to a height of 20 m, its slender trunk rarely exceeds 0.5 m in diameter. The bark exfoliates in irregular flakes. Its wing-less twigs bear comparatively large obovate to oblong leaves up to 18 cm in length [1]. The wind-pollinated petal-less flowers are produced on second-year shoots in March; the samarae are obovate < 25 mm long by 17 mm wide and ripen in April.

The tree is rare in cultivation in the West, but was evaluated by Mittempergher in Italy, who found it to have a low susceptibility to Dutch elm disease and elm leaf beetle. It also featured in elm trials conducted by the Institut Nationale de la Recherche Agronomique (INRA) on gravelly soils in the Bois de Vincennes, Paris, but most specimens were killed by drought.

12-year-old Chenmou Elm

The Morton Arboretum, at Lisle, Illinois, is home to the largest Elm collection in North America. Under study, the collection includes almost all of the 22 Elm species native to China, a dozen of which show resistance to Dutch elm disease and elm yellows. The Arboretum in past years has bred and marketed five new elm varieties resistant to Dutch elm disease.

These 12 Chinese trees are virtually unknown in the U.S., but are under close study at the arboretum. Dendrologist Emeritus and former research director Dr. George Ware, and Arboretum Assistant Director of Collections Kunso Kim are responsible for their observation and data collection. Their efforts may help ameliorate the effects of numerous maladies affecting trees around the world, such as Emerald Ash Borer, Oak wilt, Asian Longhorned Beetle, Pine Sawyer Beetle, et al.

"These and other problems underscore the urgent need for the Arboretum and others to continue seeking new species for urban use," Kim says. The average lifespan of an urban tree is fewer than 10 years, according to Ware. But "planting hardier trees increases the likelihood of a longer life span and a greener world - a goal that has never been more important than now, with climate change upon us."[2]